For the activity below select the Intro tab on the opening screen. 1. Choose the first spring on the left and hang a known mass off of it. On the previous simulation the force applied (equal and opposite to the spring force, F,) was given. What is the name of the force responsible for stretching the spring in this case? 2. How do we calculate the force identified above? Be sure to state what each variable represents and what the appropriate units are for each